Figure 2: Formation energetics of clathrate hydrates.

(a) A schematic view of Gibbs free energy as a function of reaction coordinate for the formation of sI and sII carbon monoxide hydrates, inferred from our experimental observations (Fig. 1) and binding energy calculations. The horizontal line denotes the ground state of Gibbs free energy. E_a and E_b are activation energy and binding energy, respectively. The Gibbs free energy associated with E_b is negative as binding energy is released; (b) a schematic illustration of cage occupancy in 5¹²6² and 5¹²6⁴ cages as a function of binding energy in sI and sII carbon monoxide clathrates at pressure–temperature conditions near the phase boundary.